When an electronic device is plugged in or turned on in an AC or DC electrical circuit, the electric plug's male and female connections come together and high current immediately begins to flow through the pins. Once any contact (and sometimes before contact if an arc occurs) is made on the pins, fill normal operating current flows through the device. Thus, in many electronic devices the pins are designed so that any part of the pins or socket can immediately handle the full normal operating current. If due to space (or other) constraints, the pins are not designed for an individual pin to handle the full normal operating current, there is a high probability of damage to the pins or the socket from arcing, overheating, or stress from the instant flow of full current. It is also possible that there will exist a safety hazard since many connectors designed to handle high currents have exposed metal parts allowing people to receive electric shocks or burns.
Other electronic devices include capacitors requiring initial charging once power is connected to the device. Once power is connected, the capacitors draw high current until they reach full charge. Capacitor lifespan and reliability can be improved by limiting the charging current to the capacitor. Some designs include resistors in series with the capacitors to act as current limiters, however, it is only necessary to limit current to the capacitor during initial charge up, and once fully charged, the resistor is no longer necessary, and in fact, may cause continuous power dissipation during normal operation of the device. Other designs use a relay or transistor to limit the initial charge up current, however this solution still leaves a small series resistance, and requires extra components in the design of the device, thus slightly reducing the overall reliability of the device. Still other designs use a positive temperature coefficient (PTC) device that starts out with a high resistance while cold and decreases in resistance as it heats up. However, this solution still continually dissipates enough power to keep the PTC device hot, and adds an extra component to the design of the electronic device.